Thin power storage device and production method thereof

ABSTRACT

A power storage device includes a positive electrode part including a first metallic foil layer and a positive electrode active material layer partially laminated on one surface of the first metallic foil layer, a negative electrode part including a second metallic foil layer and a negative electrode active material layer partially laminated on one surface of the second metallic foil layer, and a separator arranged between the positive electrode part and the negative electrode part. The positive electrode active material layer is arranged between the first metallic foil layer and the separator, and the negative electrode active material layer is arranged between the second metallic foil layer and the separator. The peripheral regions of the one surfaces of the first and second metallic foil layers in which the positive and negative electrode active material layers are not formed are joined via a peripheral sealing layer containing a thermoplastic resin.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure relates to a light-weighted, thinned, andspace-saved thin power storage device, and its production method.

In this disclosure, the term “aluminum” is used to express a meaningincluding Al and Al alloy, the term “copper” is used to express ameaning including Cu and Cu alloy, the term “nickel” is used to expressa meaning including Ni and Ni alloy, and the term “titanium” is used toexpress a meaning including Ti and Ti alloy. Further, in thisdisclosure, the term “metal” is used to express a meaning includingsimple metal and alloy.

Description of the Related Art

The following description of related art sets forth the inventors'knowledge of related art and certain problems therein and should not beconstrued as an admission of knowledge in the prior art.

In recent year, in accordance with the thinning and lightweighting of amobile device such as, e.g., a smart phone or a tablet terminal, as apackaging material for a lithium-ion secondary battery or alithium-polymer secondary battery to be mounted on the mobile device, inplace of a conventional metallic can, a laminated packaging material inwhich resin films are adhered on both surfaces of a metallic foil isused. In the same manner, it is being considered to mount an electriccondenser, a capacitor, etc., having a laminated packaging material as abackup power source on an IC card or an electronic device.

As a battery in which a battery main body is accommodated in a laminatedpackaging material in which resin films are adhered on both surfaces ofa metallic foil, known is a card battery in which a battery constituentmaterial comprising a laminate of a positive electrode, a separator, anda negative electrode, and electrolyte is accommodated, wherein the cardbattery is a thin battery using a laminated film which is constituted bysequentially laminating a thermoplastic resin, a metallic foil, and athermoplastic resin (see Patent Document 1: Japanese Unexamined PatentApplication Publication No. 2005-56854)

According to the thin battery disclosed by Patent Document 1, however,the electrode main body and the laminated packaging material arestructured separately, and therefore the entire thickness of the powerstorage device armored by the laminated packaging material is a total ofthe thickness of the electrode main body and the thickness of thelaminated packaging material. For this reason, it was difficult for thethin battery to be applied to an application having a thicknesslimitation or a weight limitation (an IC card, a smart phone, etc.).

Further, since it is required to provide a tab lead wire (lead wire)extended from an electrode, there is a problem that the number of partsis increased. Further, since the tab lead wire is required to be fixedat a heat-sealed portion formed at the peripheral edge of the laminatedpackaging material, there is a problem that the number of processes atthe time of production increases, resulting in a troublesome work, andthat the weight (mass) as a thin battery also increases.

The description herein of advantages and disadvantages of variousfeatures, embodiments, methods, and apparatus disclosed in otherpublications is in no way intended to limit the present invention. Forexample, certain features of the preferred described embodiments of theinvention may be capable of overcoming certain disadvantages and/orproviding certain advantages, such as, e.g., disadvantages and/oradvantages discussed herein, while retaining some or all of thefeatures, embodiments, methods, and apparatus disclosed therein.

SUMMARY OF THE INVENTION

The disclosed embodiments of the present invention have been developedin view of the above-mentioned and/or other problems in the related art.The disclosed embodiments of the present invention can significantlyimprove upon existing methods and/or apparatuses.

The embodiments of the present invention were made in view of theaforementioned technical background, and aim to provide a light-weightedand thinned thin power storage device and its production method.

To attain the aforementioned objects, some embodiments of the presentinvention provide the following means.

[1] A thin power storage device comprising:

a positive electrode part including a first metallic foil layer and apositive electrode active material layer laminated on a partial regionof one surface of the first metallic foil layer;

a negative electrode part including a second metallic foil layer and anegative electrode active material layer laminated on a partial regionof one surface of the second metallic foil layer; and

a separator arranged between the positive electrode part and thenegative electrode part,

wherein the positive electrode active material layer is arranged betweenthe first metallic foil layer and the separator, and the negativeelectrode active material layer is arranged between the second metallicfoil layer and the separator, and

wherein a peripheral region of the one surface of the first metallicfoil layer of the positive electrode part in which the positiveelectrode active material layer is not formed and a peripheral region ofthe one surface of the second metallic foil layer of the negativeelectrode part in which the negative electrode active material layer isnot formed are joined via a peripheral sealing layer containing athermoplastic resin.

[2] The thin power storage device as recited in the aforementioned Item[1],

wherein a first insulation resin film is laminated on the other surfaceof the first metallic foil layer in a manner such that a first metalexposed portion in which the first metallic foil layer is exposed, and

wherein a second insulation resin film is laminated on the other surfaceof the second metallic foil layer in a manner such that a second metalexposed portion in which the second metallic foil layer is exposedremains.

[3] The thin power storage device as recited in the aforementioned Item[2], wherein the first insulation resin film and the second insulationresin film are each formed by a heat-resistant resin stretched film.

[4] The thin power storage device as recited in any one of theaforementioned Items [1] to [3],

wherein the positive electrode active material layer is laminated on theone surface of the first metallic foil layer via a first binder layer,and the negative electrode active material layer is laminated on the onesurface of the second metallic foil layer via a second binder layer, and

wherein the first binder layer and the second binder layer are each madeof at least one binder material selected from the group consisting ofpolyvinylidene fluoride, styrene-butadiene rubber, carboxymethylcellulose sodium salt, and polyacrylonitrile.

[5] The thin power storage device as recited in any one of theaforementioned Items [1] to [4], wherein the peripheral sealing layer isformed by a thermoplastic resin unstretched film.

[6] The thin power storage device as recited in any one of theaforementioned Items [1] to [5],

wherein an electrolyte is encapsulated between the separator and thepositive electrode active material layer, and

wherein an electrolyte is encapsulated between the separator and thenegative electrode active material layer.

[7] The thin power storage device as recited in any one of theaforementioned Items [1] to [6],

wherein the first metallic foil layer is formed by an aluminum foil, and

wherein the second metallic foil layer is formed by an aluminum foil, acopper foil, a stainless steel foil, a nickel foil or a titanium foil.

[8] The thin power storage device as recited in any one of theaforementioned Items [1] to [7],

wherein a first chemical conversion film is formed at least on a surfaceof the first metallic foil layer to which the positive electrode activematerial layer is laminated, and

wherein a second chemical conversion film is formed at least on asurface of the second metallic foil layer to which the negativeelectrode active material layer is laminated.

[9] A production method of a thin power storage device, comprising:

a step of preparing a positive electrode side sheet body including afirst metallic foil layer, a positive electrode active material layerlaminated on a partial region of one surface of the first metallic foillayer, and a first thermoplastic resin layer provided at a peripheralportion of the one surface of the first metallic foil layer on which thepositive electrode active material layer is not formed;

a step of preparing a negative electrode side sheet body including asecond metallic foil layer, a negative electrode active material layerlaminated on a partial region of one surface of the second metallic foillayer, and a second thermoplastic resin layer provided at a peripheralportion of the one surface of the second metallic foil layer on whichthe negative electrode active material layer is not formed;

a step of preparing a separator; and

a step of heat-sealing the first thermoplastic resin layer of thepositive electrode side sheet body and the second thermoplastic resinlayer of the negative electrode side sheet body in a state in which thepositive electrode side sheet body and the negative electrode side sheetbody are in contact with each other via respective thermoplastic resinlayers and the separator is sandwiched by and between the positiveelectrode active material layer and the negative electrode activematerial layer.

[10] The production method of a thin power storage device as recited inthe aforementioned Item [9],

wherein the first thermoplastic resin layer is formed by a thermoplasticresin unstretched film and the second thermoplastic resin layer isformed by a thermoplastic resin unstretched film.

In some embodiments of the invention recited in the aforementioned Item[1], the first metallic foil layer constituting the positive electrodepart and the second metallic foil layer constituting the negativeelectrode part also serve a function of a packaging material of thepower storage device. In other words, the first and second metallic foillayers serve both functions of an electrode and a packaging material.For this reason, since an additional packaging material is not requiredto the above structure (a packaging material becomes unnecessary), itbecomes possible to attain lightweighting, thinning, and space-saving asa power storage device, and also possible to attain a cost reduction.

In some embodiments of the invention recited in the aforementioned item[2], it is structured such that the first insulation resin film islaminated on the other surface of the first metallic foil layer with thefirst metal exposed portion through which the first metallic foil layeris exposed remained, and the second insulation resin film is laminatedon the other surface of the second metallic foil layer with the secondmetal exposed portion through which the second metallic foil layer isexposed remained, and these insulation resin films are laminated on bothsides of the device. Therefore, sufficient insulation can be secured(except for the metal exposed portions), and physical strength can alsobe secured. For this reason, it is possible to sufficiently cope withmounting (the thin power storage device) on a portion which is requiredto have an insulation or a portion having irregularities.

Further, the existence of the first metal exposed portion electricallyconnected to the positive electrode and the second metal exposed portionelectrically connected to the negative electrode enables electrictransmission via the metal exposed portions. Thus, there is an advantagethat it becomes possible to eliminate a conventional lead wire. For thisreason, the number of parts of the thin power storage device can bereduced, and it becomes possible to attain the lightweighting.

Further, a conventional lead wire becomes unnecessary, which prevents anoccurrence of a phenomenon of intensively causing heat generation duringcharging and discharging of the power storage device around the leadwire. Further, the heat generation can be diffused (two-dimensionally)to the entirety of the thin power storage device via the first metallicfoil layer constituting the positive electrode part and the secondmetallic foil layer constituting the negative electrode part. Thisenables extension of the life of the power storage device (it becomespossible to obtain a long life power storage device). Further, since alead wire becomes unnecessary, the production cost can be reduced bythat.

In addition, like a dry cell battery, it becomes possible to employ asimple mounting method of fitting the thin power storage device into aholder.

According to some embodiments of the invention as recited in theaforementioned Item [3], the first insulation resin film and the secondinsulation resin film are each formed by a heat-resistant resinstretched film. Therefore, the strength and the formability can beimproved.

According to some embodiments of the invention as recited in theaforementioned Item [4], the binder layer made of at least one bindermaterial selected from the group consisting of polyvinylidene fluoride,styrene-butadiene rubber, carboxymethyl cellulose sodium salt, andpolyacrylonitrile is provided. The binding property between the firstmetallic foil layer and the positive electrode active material layer canbe improved, and the binding property between the second metallic foillayer and the negative electrode active material layer can also beimproved.

According to some embodiments of the invention as recited in theaforementioned Item [5], the peripheral sealing layer is formed by athermoplastic resin unstretched film, which can improve the chemicalresistance (including the resistance against the electrolyte) and alsocan improve the heat sealing performance of the peripheral sealinglayer, which can sufficiently prevent leakage of the electrolyte.

According to some embodiments of the invention as recited in theaforementioned Item [6], it is structured such that an electrolyte issealed between the separator and the positive electrode active materiallayer, and the electrolyte is sealed between the separator and thenegative electrode active material layer. Although the separator isarranged between them, electric charges can be moved between thepositive electrode and the negative electrode via the electrolyte.

According to some embodiments of the invention as recited in theaforementioned Item [7], since the first metallic foil layer is made byan aluminum foil, the application property of the positive electrodeactive material can be improved, and the lamination of the peripheralsealing layer containing the thermoplastic resin to the first metallicfoil layer can be made easy. Further, the second metallic foil layer isformed by an aluminum foil, a copper foil, a stainless steel foil, anickel foil, or a titanium foil, and therefore the application can beexpanded to various power storage devices such as a battery, acapacitor, etc.

According to some embodiments of the invention as recited in theaforementioned Item [8], the corrosion resistance of the first metallicfoil layer and the second metallic foil layer can be improved, and theadhesiveness of both the metallic foil layers can be improved.

According to some embodiments of the invention as recited in theaforementioned Item [9], a light-weighted, thinned, and space-saved highquality thin power storage device can be produced efficiently.

According to some embodiments of the invention as recited in theaforementioned Item [10], the first and second thermoplastic resinlayers are each formed by a thermoplastic resin unstretched film.Therefore, the chemical resistance (including the resistance against theelectrolyte) of the peripheral sealing layer of the thin power storagedevice can be improved, and the heat sealing performance of theperipheral sealing layer can be improve, which can sufficiently preventleakage, etc., of the electrolyte.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed embodiments of the present invention are shown by way ofexample, and not limitation, in the accompanying figures.

FIG. 1 is a perspective view showing one embodiment of a thin powerstorage device according to the present invention.

FIG. 2 is an enlarged cross-sectional view taken along the line A-A inFIG. 1.

FIG. 3 is a perspective view showing another embodiment of a thin powerstorage device according to the present invention.

FIG. 4 is an enlarged cross-sectional view taken along the line B-B inFIG. 3.

FIG. 5 is a perspective view showing one embodiment of a power storagedevice module constituted by a plurality of thin power storage devicesaccording to the present invention.

FIG. 6 is an enlarged cross-sectional view taken along the line C-C inFIG. 5.

FIG. 7 is a cross-sectional view showing one example of a productionmethod of a thin power storage device according to the presentinvention.

FIGS. 8A, 8B, and 8C are plan views showing a production method of anembodiment, wherein FIG. 8A is a plan view showing a state in which apositive electrode active material layer is formed at three portions onthe surface of the binder layer laminated on one surface of an aluminumfoil, FIG. 8B is a plan view showing a cutting position (two-dot chainline) for obtaining a positive electrode side sheet body, and FIG. 8C isa plan view showing three cut pieces in an arranged manner.

FIGS. 9A and 9B are views showing one embodiment of a power storagemodule according to the present invention, wherein FIG. 9A is aperspective view seen from the front side, and FIG. 9B is a perspectiveview seen from the rear side.

FIGS. 10A, 10B, and 10C are plan views showing a production methodaccording to Comparative Example 1, wherein FIG. 10A is a perspectiveview showing a state in which a separator is sandwiched by a positiveelectrode and a negative electrode, FIG. 10B is a perspective viewshowing a state in which a battery main body is sandwiched from bothsides thereof by packaging materials, and FIG. 10C is a perspective viewshowing a thin power storage device of Comparative Example 1 obtained byheat-sealing the peripheral edges of a pair of packaging materials.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

In the following paragraphs, some embodiments of the invention will bedescribed by way of example and not limitation. It should be understoodbased on this disclosure that various other modifications can be made bythose in the art based on these illustrated embodiments.

A first embodiment of a thin power storage device according to thepresent invention is shown in FIGS. 1 and 2. This thin power storagedevice 1 is equipped with a positive electrode part 22, a negativeelectrode part 23, and a separator (see FIG. 2). The separator 21 isarranged between the positive electrode part 22 and the negativeelectrode part 23.

The positive electrode part 22 includes a first metallic foil layer 2and a positive electrode active material layer 3 laminated on a partialregion of one surface (separator side surface) of the first metallicfoil layer 2. In this embodiment, the positive electrode active materiallayer 3 is laminated on the central portion (region excluding theperipheral portion) of one surface (separator side surface) of the firstmetallic foil layer 2. Further, in this embodiment, a binder layer 7 islaminated on the entire surface of the one surface of the first metallicfoil layer 2. That is, in this embodiment, the positive electrode activematerial layer 3 is laminated on the one surface (separator sidesurface) of the first metallic foil layer 2 via the binder layer 7.

The negative electrode part 23 includes a second metallic foil layer 12and a negative electrode active material layer 13 laminated on a partialregion of one surface (separator side surface) of the second metallicfoil layer 12. In this embodiment, the negative electrode activematerial layer 13 is laminated on the central portion (region excludingthe peripheral portion) of one surface (separator side surface) of thesecond metallic foil layer 12. Further, in this embodiment, a binderlayer 17 is laminated on the entire surface of the one surface(separator side surface) of the second metallic foil layer 12. That is,in this embodiment, the negative electrode active material layer 13 islaminated on the one surface (separator side surface) of the secondmetallic foil layer 12 via the binder layer 17.

The positive electrode active material layer 3 is arranged between thefirst metallic foil layer 2 and the separator 21, and the negativeelectrode active material layer 13 is arranged between the secondmetallic foil layer 12 and the separator 21 (see FIG. 2).

At the peripheral portion of the one surface (separator 21 side surface)of the first metallic foil layer 2 of the positive electrode part 22,there exists a region on which the positive electrode active materiallayer is not formed. While, at the peripheral portion of the one surface(separator 21 side surface) of the second metallic foil layer 12 of thenegative electrode part 23, there exists a region on which the negativeelectrode active material layer is not formed. Thus, a peripheral regionof the one surface of the first metallic foil layer 2 of the positiveelectrode part 22 on which the positive electrode active material layeris not formed and a peripheral region of the one surface of the secondmetallic foil layer 12 of the negative electrode part 23 on which thenegative electrode active material layer is not formed are joined andsealed via a peripheral sealing layer 31 containing a thermoplasticresin (see FIG. 2). The peripheral portion of the separator 21 isentered into and engaged with the intermediate portion of the innerperipheral surface of the peripheral sealing layer 31 in the heightdirection (thickness direction) (see FIG. 2).

In this embodiment, at the peripheral region of the binder layer 7laminated on the one surface of the first metallic foil layer 2 of thepositive electrode part 22 on which the positive electrode activematerial layer is not formed, a first peripheral adhesive agent layer 6is laminated. At the peripheral region of the binder layer 17 laminatedon the one surface of the second metallic foil layer 12 of the negativeelectrode part 23 on which the negative electrode active material layeris not formed, a second peripheral adhesive agent layer 16 is laminated.A structure is adopted in which both the adhesive agent layers 6 and 16are joined and sealed vial the peripheral sealing layer 31 (see FIG. 2).

An electrolyte 5 is encapsulated between the separator 21 and thepositive electrode active material layer 3. Further, an electrolyte 15is encapsulated between the separator 21 and the negative electrodeactive material layer 13 (see FIG. 2). The peripheral region of thefirst metallic foil layer 2 on which the positive electrode activematerial layer is not formed and the peripheral region of the secondmetallic foil layer 12 on which the negative electrode active materiallayer is not formed are joined and sealed via the peripheral sealinglayer 31. Therefore, leakages of the electrolytes 5 and 15 can beprevented. That is, within the sealed space surrounded by the peripheralsealing layer 31, the first peripheral adhesive agent layer 6 and thesecond peripheral adhesive agent layer 16 between the binder layer 7arranged at the inner side of the first metallic foil layer 2 and thebinder layer 17 arranged at the inner surface side of the secondmetallic foil layer 12, in the order from the first metallic foil layer2 side, the positive electrode active material layer 3, the electrolyte5, the separator 21, the electrolyte 15, and the negative electrodeactive material layer 13 are arranged and sealed (see FIG. 2).

In the thin power storage device 1 having the aforementioned structure,the first metallic foil layer 2 structuring the positive electrode part22 and the second metallic foil layer 12 structuring the negativeelectrode part 23 also serve a function as a packaging material of thepower storage device. That is, the first and second metallic foil layersserve both functions of an electrode and a packaging material. For thisreason, since a packaging material is not required in addition to theaforementioned structure (a packaging material becomes unnecessary), asa thin power storage device, it becomes possible to attainlightweighting, thinning, and space-saving, and also becomes possible toattain a cost reduction.

A second embodiment (preferred embodiment) of a thin power storagedevice according to the present invention is shown in FIGS. 3 and 4.This thin power storage device 1 has the structure of the aforementionedfirst embodiment, and further has the following structure.

That is, in a manner such that a first metal exposed portion 9 in whichthe first metallic foil layer 2 is exposed remains, the first insulationresin film 8 is laminated on the other surface (the surface opposite tothe separator side surface) of the first metallic foil layer 2, and thata second metal exposed portion 19 in which the second metallic foillayer 12 is exposed remains, the second insulation resin film 18 islaminated on the other surface (the surface opposite to the separatorside surface) of the second metallic foil layer 12. In this embodiment,in a manner such that the first metal exposed portion 9 through whichthe first metallic foil layer is exposed remains, the first insulationresin film 8 is laminated on the other surface (the surface opposite tothe separator side surface) of the first metallic foil layer 2 via athird adhesive agent layer 41. Further, in a manner such that the secondmetal exposed portion 19 through which the second metallic foil layer 12is exposed remains, the second insulation resin film 18 is laminated onthe other surface (the surface opposite to the separator side surface)of the second metallic foil layer 12 via a fourth adhesive agent layer42. Further, in this embodiment, the first metal exposed portion 9 isprovided at the central region of the other surface of the firstmetallic foil layer 2, and the second metal exposed portion 19 isprovided at the central region of the other surface of the secondmetallic foil layer 12 (see FIGS. 3 and 4).

In the thin power storage device 1 of this second embodiment, in thesame manner as in the first embodiment, the first and second metallicfoil layers serve both functions of an electrode and a packagingmaterial. For this reason, a packaging material is not required inaddition to the structure (that is, a packaging material becomesunnecessary). As a result, as a thin power storage device, it becomespossible to attain lightweighting, thinning, and space-saving, and alsobecomes possible to attain a cost reduction.

Further, since the insulation resin films 8 and are laminated on bothsides of the device, sufficient insulation can be secured (except forthe metal exposed portions), and sufficient physical strength can alsobe secured. Therefore, it is sufficiently possible to mount the thinpower storage device 1 of the present invention on a portion requiringinsulation properties and/or a portion with irregularities.

Further, the existence of the first metal exposed portion 9 electricallyconnected to the positive electrode and the second metal exposed portion19 electrically connected to the negative electrode enables electrictransmission via the metal exposed portions 9 and 19. Therefore, thereis an advantage that it becomes possible to eliminate the necessity (theuse) of a conventional lead wire (e.g., tab leads 131 and 141 shown inFIGS. 10A, 10B, and 10C, etc.). For this reason, the number of parts ofthe thin power storage device can be reduced, and it becomes possible toattain the lightweighting.

Further, a conventional lead wire becomes unnecessary, which prevents aphenomenon that heat generation during charging and discharging of thepower storage device intensively occurs around the lead wire. Further,heat generation can be diffused to the entirety of both surfaces of thethin power storage device 1 via the first metallic foil layer 2constituting the positive electrode part 22 and the second metallic foillayer 12 constituting the negative electrode part 23. This enables anextension of the life of the power storage device 1 (that is, a longlife power storage device can be obtained). Further, since a lead wirebecomes unnecessary, the production cost can be reduced by that.

In addition, like a dry cell battery, it becomes possible to employ asimple mounting method of fitting the thin power storage device 1 of thepresent invention into a holder.

In the present invention, the first metallic foil layer 2 is notespecially limited, but is preferably made of an aluminum foil. Thethickness of the first metallic foil layer 2 is preferably set to 7 μmto 150 μm. Especially, in the case of being used as a thin lithiumsecondary battery, the first metallic foil layer 2 is preferably made ofa hard aluminum foil having a thickness of 7 μm to 50 μm.

The positive electrode active material layer 3 is not specificallylimited, but can be formed by, e.g., a mixed composition in which salt(such as, e.g., lithium cobalt oxide, lithium nickel oxide, lithium ironphosphate, lithium manganese oxide, etc.) is added to a binder, such as,e.g., polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR),carboxymethyl cellulose sodium salt (CMC), polyacrylonitrile (PAN), etc.The thickness of the positive electrode active material layer 3 ispreferably set to 2 μm to 300 μm.

The positive electrode active material layer 3 may further includes aconductive assistant such as, e.g., carbon black, carbon nanotube (CNT),etc.

The binder layer 7 is not specifically limited, but can be, for example,a layer formed by polyvinylidene fluoride (PVDF), styrene-butadienerubber (SBR), carboxymethyl cellulose sodium salt (CMC),polyacrylonitrile (PAN), etc., which can be formed by applying it to theone surface (separator 21 side surface) of the first metallic foil layer2.

The binder layer 7 may further include a conductive assistant such as,e.g., carbon black, carbon nanotube (CNT), etc., to improve theelectrical conductivity between the first metallic foil layer 2 and thepositive electrode active material layer 3.

The thickness of the binder layer 7 is preferably set to 0.2 μm to 10μm. By setting to 10 μm or less, it becomes possible to control theincrease of the internal resistance of the power storage device 1 asmuch as possible.

The binder layer 7 is not required to be provided, but is preferablyprovided between the first metallic foil layer 2 and the positiveelectrode active material layer 3 to improve the binding propertybetween the first metallic foil layer 2 and the positive electrodeactive material layer 3.

The first peripheral adhesive agent layer 6 is not specifically limited,but can be exemplified by an adhesive layer formed by apolyurethane-based adhesive agent, an acrylic adhesive agent, anepoxy-based adhesive agent, a polyolefin-based adhesive agent, anelastomeric adhesive agent, a fluorine-based adhesive agent, etc. Amongthem, it is preferable to use an acrylic adhesive agent, or apolyolefin-based adhesive agent. In this case, the electrolyteresistance and the water vapor barrier property can be improved.Further, it is especially preferable that the first peripheral adhesiveagent layer 6 is a layer formed by a two-part curing type olefin-basedadhesive agent. In the case of using a two-part curing type olefin-basedadhesive, the possible deterioration of the adhesiveness due to theswelling of the electrolyte can be prevented sufficiently. In caseswhere the power storage device 1 constitutes a battery, the firstperipheral adhesive agent layer 6 is preferably made of an acid-modifiedpolypropylene adhesive agent, or an acid-modified polyethylene adhesiveagent. The thickness of the first peripheral adhesive agent layer 6 ispreferably set to 0.5 μm to 5 μm.

In the present invention, the second metallic foil layer 12 is notespecially limited, but is preferably made by an aluminum foil, a copperfoil, a stainless steel foil, a nickel foil, or a titanium foil. Thethickness of the second metallic foil layer 12 is preferably set to 7 μmto 50 μm.

The negative electrode active material layer 13 is not specificallylimited, but can be formed by, e.g., a mixed composition in which anadditive (such as, e.g., graphite, lithium titanium acid, Si-basedalloy, tin-based alloy, etc.) is added to a binder, such as, e.g.,polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR),carboxymethyl cellulose sodium salt (CMC), polyacrylonitrile (PAN), etc.The thickness of the negative electrode active material layer 13 ispreferably set to 1 μm to 300 μm.

The negative electrode active material layer 13 may further include aconductive assistant such as carbon black, carbon nanotube (CNT), etc.

In the case of forming the negative electrode active material layer 13or the positive electrode active material layer 3 by applying the activematerial, by applying the active material with the non-active materialapplying portion (peripheral portion, etc.) being previously masked by amasking tape, an active material layer can be formed without adheringthe active material on the non-active material applying portion(peripheral portion, etc.). As a masking tape, a tape on which anadhesive is applied to a film such as, e.g., a polyester resin film, apolyethylene resin film, a polypropylene resin film, etc., can be used.

The binder layer 17 is not specifically limited, but can be, forexample, a layer formed by polyvinylidene fluoride (PVDF),styrene-butadiene rubber (SBR), carboxymethyl cellulose sodium salt(CMC), polyacrylonitrile (PAN), etc., which can be formed by, forexample, applying it to the one surface (separator side surface) of thesecond metallic foil layer 12.

The binder layer 17 may further include a conductive assistant such as,e.g., carbon black, carbon nanotube (CNT), etc., to improve theelectrical conductivity between the second metallic foil layer 12 andthe negative electrode active material layer 13.

The thickness of the binder layer 17 is preferably set to 0.2 μm to 10μm. By setting to 10 μm or less, it becomes possible to control that thebinder itself increases the internal resistance of the power storagedevice 1 as much as possible.

The binder layer 17 is not required to be provided, but is preferablyprovided between the second metallic foil layer 12 and the negativeelectrode active material layer 13 to improve the binding propertybetween the second metallic foil layer 12 and the negative electrodeactive material layer 13.

The second peripheral adhesive agent layer 16 is not specificallylimited, but can be exemplified by an adhesive layer formed by, forexample, a polyurethane-based adhesive agent, an acrylic adhesive agent,an epoxy-based adhesive agent, a polyolefin-based adhesive agent, anelastomeric adhesive agent, a fluorine-based adhesive agent, etc. Amongthem, it is preferable to use an acrylic adhesive agent, or apolyolefin-based adhesive agent. In this case, the electrolyteresistance and the water vapor barrier property can be improved.Further, it is especially preferable that the second peripheral adhesiveagent layer 16 is a layer formed by a two-part curing type olefin-basedadhesive agent. In the case of using a two-part curing type olefin-basedadhesive agent, the possible deterioration of the adhesiveness due tothe swelling of the electrolyte can be sufficiently prevented. In caseswhere the power storage device 1 constitutes a battery, the secondperipheral adhesive agent layer 16 is preferably made of anacid-modified polypropylene adhesive agent, or an acid-modifiedpolyethylene adhesive agent. The thickness of the second peripheraladhesive agent layer 16 is preferably set to 0.5 μm to 5 μm.

In the aforementioned embodiment, the peripheral sealing layer 31 (theperipheral sealing layer containing a thermoplastic resin) is formed byoverlapping the first thermoplastic resin layer 4 laminated on theperipheral portion of one surface of the first metallic foil layer 2 andthe second thermoplastic resin layer 14 laminated on the peripheralportion of one surface of the second metallic foil layer 12 andfusion-welding them by heat. As the first thermoplastic resin layer 4,it is preferable to use a layer formed by a thermoplastic resinunstretched film. Further, as the second thermoplastic resin layer 14,it is preferable to use a layer formed by a thermoplastic resinunstretched film.

The thermoplastic resin unstretched films 4 and 14 is not specificallylimited, but is preferably structured by an unstretched film made of atleast one type of a thermoplastic resin selected from the groupconsisting of polyethylene, polypropylene, olefin copolymer, theiracid-modified product and ionomer.

The thickness of the thermoplastic resin unstretched films 4 and 14 ispreferably set to 20 μm to 150 μm.

The separator 21 is not specifically limited, but can be exemplified by:for example,

a polyethylene separator;

a polypropylene separator;

a separator formed by a multi-layer film made of a polyethylene film anda polypropylene film; and

a separator structured by a wet or dry porous film on which aheat-resistant inorganic substance such as ceramic is applied to one ofthe aforementioned separator.

The thickness of the separator 21 is preferably set to 5 μm to 50 μm.

As the electrolytes 5 and 15, it is not specifically limited. However,it is preferable to use a mixed non-aqueous electrolyte containing atleast two types of electrolytes selected from the group consisting ofethylene carbonate, propylene carbonate, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate and dimethoxyethane, and lithiumsalt. As the lithium salt, it is not specifically limited, but can beexemplified by, for example, lithium hexafluorophosphate, lithiumtetrafluoroborate or the like. As the electrolytes 5 and 15, it ispossible to use an electrolyte in which the aforementioned mixednon-aqueous electrolyte is gelled with polyvinylidene fluoride (PVDF),polyethylene oxide (PEO), etc.

The separator 21 and the electrolytes 5 and 15 are encapsulated in asealed manner in the space between the first metallic foil layer 2 andthe second metallic foil layer 12 in such a manner that the periphery issurrounded by the peripheral sealing layer 31, etc. (see FIGS. 2 and 4).This prevents leakage of the electrolytes.

As the first insulation resin film 8 and the second insulation resinfilm 18, it is not specifically limited, but is preferable to use astretched polyamide film (a stretched nylon film, etc.) or a stretchedpolyester film. Among them, it is especially preferable to use abiaxially stretched polyamide film (biaxially stretched nylon film orthe like), a biaxially stretched polybutylene terephthalate (PBT) film,a biaxially stretched polyethylene terephthalate (PET) film or abiaxially stretched polyethylene naphthalate (PEN) film. The firstinsulation resin film 8 and the second insulation resin film 18 can beformed by a single layer, or can be formed by a multi-layer made of, forexample, a stretched polyester film/a stretched polyamide film (amulti-layer made of a stretched PET film/a stretched nylon film, etc.).

In the first insulation resin film 8, an opening 8X for securing thefirst metal exposed portion 9 is partially formed (see FIG. 4). In thisembodiment, the opening 8 X is provided at the central portion of thefirst insulation resin film 8, but the position is not limited to theabove. The plan view shape of the opening 8X is not limited to arectangular shape.

In the same manner, in the second insulation resin film 18, an opening18X for securing the second metal exposed portion 19 is partiallyprovided (see FIG. 4). In this embodiment, the opening 18X is providedat the central portion of the second insulation resin film 18, but theposition is not limited to the above. The plan view shape of the opening18X is not limited to a rectangular shape.

The thickness of the first insulation resin film 8 and the thickness ofthe second insulation resin film 18 are each preferably set to 0.02 mmto 0.1 mm.

In the case of providing the third adhesive agent layer 41 and thefourth adhesive agent layer 42, as these adhesive agents 41 and 42, itis no specifically limited, but it is preferable to use at least onetype of an adhesive agent selected from the group consisting of apolyester urethane-based adhesive agent and a polyether urethane-basedadhesive agent. As the polyester urethane-based adhesive agent, forexample, a two-part curing type polyester urethane-based resin adhesiveagent containing a polyester resin as a main agent and a polyfunctionalisocyanate compound as a curing agent is exemplified. As the polyetherurethane-based adhesive agent, for example, a two-part curing typepolyether urethane-based resin adhesive agent containing a polyetherresin as a main agent and a polyfunctional isocyanate compound as acuring agent is exemplified. The thickness of the third adhesive agentlayer 41 and the thickness of the fourth adhesive agent layer 42 areeach preferably set to 0.5 μm to 5 μm. It is preferred that the thirdadhesive agent 41 is applied to the other surface of the first metallicfoil layer 2 (the surface opposite to the separator side) and then thefirst insulation resin film 8 is adhered thereto and integrally bondedwith each other. Further, it is preferred that the fourth adhesive agent42 is applied to the other surface of the second metallic foil layer 12(the surface opposite to the separator side) and then the secondinsulation resin film 18 is adhered thereto and integrally bonded witheach other.

Since the adhesive agent non-applied portions of the third adhesiveagent layer 41 and the fourth adhesive agent layer 42 (regionscorresponding to the openings 8X and 18X) look different in glossinessfrom the adhesive agent applied region even observed through theinsulation resin film (heat-resistant resin stretched film, etc.), theposition and the shape of the adhesive agent non-applied portion can bedistinguished from the outside even in a state in which an insulationresin film with no opening is adhered thereon. Thus, by removing theportion of the adhered insulation resin film corresponding to theadhesive agent non-applied portion to thereby form the openings 8X and18X, it becomes possible to form a structure in which the metal exposedportions 9 and 19 are exposed. For example, by irradiating a laser tothe periphery of the adhesive agent non-applied portion of the adheredinsulation resin film to thereby cut the part of the insulation resinfilm corresponding to the adhesive agent non-applied portion to form theopenings 8X and 18X, it becomes possible to form a structure in whichthe metal exposed portions 9 and 19 are exposed.

Further, in the third adhesive agent layer 41 and the fourth adhesiveagent layer 42, a coloring agent such as an organic pigment, aninorganic pigment, a coloring matter, etc., can be added to theaforementioned adhesive agent in a range of 0.1 parts by mass to 5 partsby mass with respect to the resin component 100 parts by mass. As theorganic pigment, it is not specifically limited, but, for example, anazo pigment such as lake red, naphthols, hansa yellow, disazo yellow,benzimidazolone, etc., a polycyclic pigment such as quinophthalone,isoindoline, pyrrolo-pyrrole, dioxazine, phthalocyanine blue,phthalocyanine green, etc., a lake pigment such as lake red C, watchingred, etc., can be exemplified. Further, as the aforementioned inorganicpigment, it is not specifically limited, but, for example, carbon black,oxide titanium, calcium carbonate, kaolin, iron oxide, zinc oxide, etc.,can be exemplified. Further, as the aforementioned coloring matter, itis not specifically limited, but, for example, yellow dyes such astrisodium salt (Yellow No. 4), etc., red dyes such as disodium salt (RedNo. 3), etc., blue dyes such as disodium salt (Blue No. 1), etc., can beexemplified.

Further, regardless of the presence or absence of the addition ofcoloring agents, by adhering a transparent insulation resin film(heat-resistant resin stretched film, etc.), it becomes possible toreadily discriminate the adhesive agent non-applied portion. Bystructuring such that the coloring agent is added to the adhesive agentof the third adhesive agent layer 41 and the fourth adhesive agent layer42 and adhering a transparent insulation resin film (heat-resistantresin stretched film, etc.), it becomes extremely easy to discriminatethe adhesive agent non-applied portion.

In the present invention, it is preferable that a chemical conversionfilm is formed at least on the surface of the first metallic foil layer2 to which the positive electrode active material layer 3 is laminated.Further, in the same manner, it is preferable that a chemical conversionfilm is formed at least on the surface of the second metallic foil layer12 to which the negative electrode active material layer 13 islaminated. The chemical conversion film is a film which is formed bysubjecting a surface of a metallic foil to a chemical conversiontreatment, and such a chemical conversion treatment sufficientlyprevents corrosion of the metallic foil surface due to contents(electrolyte, etc.).

For example, the following treatments are executed to subject themetallic foil to a chemical conversion treatment. Any one of thefollowing aqueous solutions 1) to 3) is applied to the degreased surfaceof the metallic foil and then dried to thereby execute a chemicalconversion treatment.

1) an aqueous solution of a mixture containing:

phosphoric acid;

chromic acid; and

at least one compound selected from the group consisting of metal saltof fluoride and nonmetal salt of fluoride

2) an aqueous solution of a mixture containing:

phosphoric acid;

at least one resin selected from the group consisting of acrylic resin,chitosan derivative resin and phenolic resin; and

at least one compound selected from the group consisting of chromic acidand chromium (III) salt.

3) an aqueous solution of a mixture containing:

phosphoric acid;

at least one resin selected from the group consisting of acrylic resin,chitosan derivative resin and phenolic resin;

at least one compound selected from the group consisting of chromic acidand chromium (III) salt; and

at least one compound selected from the group consisting of metal saltof fluoride and nonmetal salt of fluoride.

The chemical conversion film is preferable that the chromium depositionamount (per one side) is 0.1 mg/m² to 50 mg/m², more specifically 2mg/m² to 20 mg/m².

Next, a preferred structure of the thin power storage device in the caseof using the thin power storage device 1 of the present invention as anelectric double layer capacitor will be explained, but it should benoted that the explanation is merely directed to a preferred structureand the present invention is not limited to the exemplified structure.

That is, in the case of being used as an electric double layercapacitor, the first metallic foil layer 2 and the second metallic foillayer 12 are each preferably made of a hard aluminum foil having athickness of 7 μm to 50 μm.

The positive electrode active material layer 3 and the negativeelectrode active material layer 13 are not specifically limited, but itis preferred to contain a conductive agent such as carbon black, carbonnanotube (CNT), etc.

As the separator 21, it is not specifically limited, but a porous polycellulose membrane having a thickness of 5 μm to 100 μm, a nonwovenfabric having a thickness of 5 μm to 100 μm, etc., can be preferablyused.

As the electrolytes 5 and 15, it is not specifically limited, but ispreferred to use an electrolyte containing water, at least one organicsolvent selected from the group consisting of ethylene carbonate,propylene carbonate, dimethyl carbonate, ethyl methyl carbonate andacetonitrile, and at least one salt selected from the group consistingof lithium hexafluorophosphate, lithium tetrafluoroboric acid andtetrafluoroborate quaternary ammonium salt. As the quaternary ammoniumsalt, for example, tetramethyl ammonium salt can be exemplified.

The preferred structure of the thin power storage device of the presentinvention in the case of being used as an electric double layercapacitor was explained above. The followings are explanations,including an explanation directed to all other applications other thanan electric double layer capacitor.

The thin power storage device 1 of the present invention is normally setto 0.08 mm to 0.3 mm in thickness. Among them, the thickness of the thinpower storage device 1 is preferably set to 0.1 mm to 0.2 mm.

Next, a power storage device module structured using a thin powerstorage device 1 of the present invention will be explained. Oneembodiment of the power storage device module 50 is shown in FIGS. 5 and6.

The power storage device module 50 has a structure in which a pluralityof thin power storage devices 1 of the present invention are laminated(stacked and overlapped) in a thickness direction (see FIGS. 5 and 6).In the power storage device module 50 of this embodiment, a conductiveresin is applied to the first metal exposed portion 9 and the secondmetal exposed portion 19 of each thin power storage device 1. That is,in each thin power storage device, the positive electrode sideconductive layer 51 containing a conductive resin is formed on thesurface of the first metal exposed portion 9, and the negative electrodeside conductive layer 52 containing a conductive resin is formed on thesurface of the second metal exposed portion 19 (see FIG. 6). Thus,according to the power storage device module 50, in the adjacent thinpower storage devices 1, the positive electrode side conductive layer 51of one power storage device 1 and the negative electrode side conductivelayer 52 of the other power storage device 1 are in well-contact witheach other, structuring a series connection of a plurality of thin powerstorage devices 1 (see FIG. 6). As the conductive resin, it is notspecifically limited, but for example, a resin containing carbon can beexemplified.

In the aforementioned embodiment, it is structured that a conductiveresin is applied to the metal exposed portions 9 and 19. However, thepresent invention is not specifically limited to such a structure, andallows the structure that a plurality of metallic foils (aluminum foils,stainless steel foils, copper foils, nickel foils, etc.) having athickness of 100 μm or less are laminated. That is, it can be structuredthat the positive electrode side conductive layer 51 made of a metallicfoil is formed on the surface of the first metal exposed portion 9, andthe negative electrode side conductive layer 52 made of a metallic foilis formed on the surface of the second metal exposed portion 19.

Since the positive electrode side conductive layer 51 and the negativeelectrode side conductive layer 52 are provided as explained above,there is an advantage that a sufficient electrical conduction statebetween adjacent power storage devices 1 can be secured by simplyarranging them in a laminated manner.

Alternatively, without providing such conductive layers 51 and 52, inthin power storage devices 1 adjacent to each other in a thicknessdirection, it can be structured such that a plurality of thin powerstorage devices 1 are connected in series with the first metal exposedportion 9 of one of the power storage devices 1 and the second metalexposed portion 19 of the other power storage device 1 being connected.When the thickness of the insulation resin film layers 8 and 18 issmall, a sufficient electrical conduction state can be secured betweenthe adjacent power storage devices 1 even without providing the positiveelectrode side conductive layer 51 and the negative electrode sideconductive layer 52.

Next, a power storage device module 50 (see FIGS. 5 and 6) in which aplurality of thin power storage devices 1 of the present invention arelaminated in the thickness direction will be explained.

The power storage device module 50 has a structure in which a pluralityof thin power storage devices 1 are laminated, and therefore the modulecan be deformed. For example, it is possible to make the power storagedevice module 50 into a cylindrical shape by bending it, and alsopossible to make the power storage device module 50 into a cylindricalshape by more compactly bending it so as to be wound in plural times. Itis also possible to adopt a configuration described below (see FIGS. 9Aand 9B) by taking advantage of such characteristics of the power storagedevice module 50.

In FIGS. 9A and 9B, the power storage device 1 is formed into a longrectangular shape, and the first metal exposed portion 9 and the secondmetal exposed portion 19 are provided at the longitudinal end portion ofthe power storage device 1. Other structures are the same as those ofthe power storage device shown in FIGS. 5 and 6. In FIGS. 9A and 9B, thepower storage device module 50 in which a plurality of thin powerstorage devices 1 are laminated in the thickness direction are wound andformed into a cylindrical shape. Since the first metal exposed portion 9and the second metal exposed portion 19 are provided at the longitudinalend portion of the power storage device 1, it is easy to attain aconnection to a terminal (positive electrode side connection terminal,negative electrode side connection terminal) of an equipment (anelectronic cigarette, a penlight, etc.). Further, since the externalsurfaces of the module 50 are formed by the insulation resin films 8 and18, sufficient insulation properties can be secured.

Next, one example of a production method of the thin power storagedevice 1 according to the present invention will be explained.Initially, the positive electrode side sheet body 61, the negativeelectrode side sheet body 62, and the separator 21 are prepared (seeFIG. 7).

That is, a positive electrode side sheet body 61 is prepared in whichthe positive electrode active material layer 3 is laminated on thepartial region of one surface of the first metallic foil layer 2 via thebinder layer 7, the first thermoplastic resin layer 4 is laminated onthe peripheral portion of the binder layer 7 laminated on the onesurface of the first metallic foil layer 2 in which the positiveelectrode active material layer is not formed via the first peripheraladhesive agent layer 6, and the first insulation resin film layer 8 islaminated on the other surface of the first metallic foil layer 2 viathe third adhesive agent layer 41 with the first metal exposed portion 9through which the first metallic foil layer 2 is exposed remained (seeFIG. 7). The first thermoplastic resin layer 4 is preferably formed by athermoplastic resin unstretched film. Further, the first insulationresin film layer 8 is preferably formed by a heat-resistant resinstretched film.

Further, a negative electrode side sheet body 62 is prepared in whichthe negative electrode active material layer 13 is laminated on thepartial region of one surface of the second metallic foil layer 12 viathe binder layer 17, the second thermoplastic resin layer 14 islaminated on the peripheral portion of the binder layer 17 laminated onthe one surface of the second metallic foil layer 12 in which thenegative electrode active material layer is not formed via the secondperipheral adhesive agent layer 16, and the second insulation resin filmlayer 18 is laminated on the other surface of the second metallic foillayer 12 via the fourth adhesive agent layer 42 with the second metalexposed portion 19 through which the second metallic foil layer 12 isexposed remained (see FIG. 7). The second thermoplastic resin layer 14is preferably formed by a thermoplastic resin unstretched film. Further,the second insulation resin film layer 18 is preferably formed by aheat-resistant resin stretched film.

Further, the separator 21 is prepared. Thus, the positive electrode sidesheet body 61 and the negative electrode side sheet body 62 are broughtinto contact with each other at the respective thermoplastic resinlayers 4 and 14, and the separator 21 is arranged between the positiveelectrode active material layer 3 and the negative electrode activematerial layer 13. The peripheral portions of the overlapped positiveelectrode side sheet body 61 and negative electrode side sheet body 62are sandwiched and pressed using heated plates, etc., to therebyheat-seal the first thermoplastic resin layer 4 and the secondthermoplastic resin layer 14.

The aforementioned heat-sealing is performed as follows. Three sides ofthe peripheral portions of the overlapped positive electrode side sheetbody 61 and negative electrode side sheet body 62 among the four sidesthereof are initially heat-sealed to perform provisional sealing.Subsequently, electrolytes 5 and 15 are injected between the separator21 and the positive electrode active material layer 3 and between theseparator 21 and the negative electrode active material layer 13 fromthe remaining non-sealed side. Thereafter, the remaining non-sealed sideis sandwiched and pressed by a pair of heated plates from above andbelow to completely seal and join the four sides to thereby obtain athin power storage device 1 of the present invention shown in FIGS. 3and 4. In the obtained thin power storage device 1, the first metalexposed portion 9 is exposed through the opening 8X at the centralportion of the first insulation resin film layer 8 and the second metalexposed portion 19 is exposed through the opening 18X at the centralportion of the second insulation resin film layer 18 (see FIGS. 3 and4).

The aforementioned production method is a mere one example, and thepresent invention is not limited to the production method.

EXAMPLES

Next, concrete examples of the present invention will be explained, butthe present invention is not specifically limited to these examples.

Example 1 (Production of Positive Electrode Side Sheet Body 61)

After applying a binder solution in which polyvinylidene fluoride (PVDF)as a binder was dissolved in a dimethylformamide (DMF) as a solvent toone surface (entire surface) of a hard aluminum foil (A1100 hardaluminum foil classified into JIS H4160) having a length 20 cm, a width30 cm and a thickness 15 μm, it was dried at 100° C. for 30 seconds toform a binder layer 7 having a thickness of 0.5 μm after drying.

After applying a paste in which 60 parts by mass of a positive electrodeactive material having lithium cobalt oxide as a main component, 10parts by mass of polyvinylidene fluoride (PVDF) as a binder and anelectrolyte retention agent, 5 parts by mass of acetylene black(conductive material), and parts by mass of N-methyl-2-pyrrolidone (NMP)(organic solvent) were kneaded and dispersed at three portions of thesurface of the binder layer 7 with the size of 75 mm×44 mm, it was driedat 100° C. for 30 minutes, and then hot-press was performed. Thus, apositive electrode active material layer 3 having a density of 4.8 g/cm³and a thickness of 30.2 μm after drying was formed (see FIG. 8A).

Next, after masking the positive electrode active material layer 3 byadhering polyester adhesive tapes having the same size to three portionsof the positive electrode active material layer 3, a two-part curingtype olefin adhesive agent (first peripheral adhesive agent layer) 6 wasapplied to form a thickness of 2 μm on a masked side surface, it wasdried at 100° C. for 15 seconds. Subsequently, a non-stretchedpolypropylene film 4A having a thickness of 25 μm was further adhered onthe first peripheral adhesive agent and left for three days in aconstant temperature reservoir of 40° C. to perform curing. Thereafter,at the position corresponding to the outer periphery of the polyesteradhesive tape (outer periphery of the positive electrode active materiallayer 3), only the non-stretched polypropylene film layer 4A was cut.Then, the non-stretched polypropylene film (only the inner portion ofthe cut portion; only the region corresponding to the adhesive tape) wasremoved together with the polyester adhesive tape, so that the surfaceof the positive electrode active material layer 3 was exposed (see FIG.8B).

Next, three pieces of positive electrode side sheet bodies 61 eachhaving a size of 85 mm×54 mm (see FIG. 8C, FIG. 7) were produced bycutting along the position (position corresponding to the two-dot chainline in FIG. 8B) positioned outward by 5 mm from the outer periphery ofthe exposed surface of the positive electrode active material layer 3.

The width M of the first thermoplastic resin layer 4 formed by thenon-stretched polypropylene film was 5 mm (see FIG. 8C).

(Production of Negative Electrode Side Sheet Body 62)

After applying a binder solution in which polyvinylidene fluoride (PVDF)as a binder was dissolved in a dimethylformamide (DMF) as a solvent toone surface (entire surface) of a hard copper foil (C1100R hard copperfoil classified into JIS H3100) having a length 20 cm, a width 30 cm anda thickness 15 μm, it was dried at 100° C. for 30 seconds to form abinder layer 17 having a thickness of 0.5 μm after drying.

After applying a paste in which 57 parts by mass of a negative electrodeactive material having carbon powder as a main component, 5 parts bymass of polyvinylidene fluoride (PVDF) as a binder and electrolyteretention agent, 10 parts by mass of a copolymer of hexafluoropropyleneand maleic anhydride, 3 parts by mass of acetylene black (conductivematerial), and 25 parts by mass of N-methyl-2-pyrrolidone (NMP) (organicsolvent) were kneaded and dispersed at three portions of the surface ofthe binder layer 17 with the size of 75 mm×44 mm, it was dried at 100°C. for 30 minutes, and then hot-press was performed. Thus, a negativeelectrode active material layer 13 having a density of 1.5 g/cm³ and athickness of 20.1 μm after drying was formed.

Next, after masking the negative electrode active material layer 13 byadhering polyester adhesive tapes having the same size to three portionsof the negative electrode active material layer 13, a two-part curingtype olefin adhesive agent (second peripheral adhesive agent layer) 16was applied to form a thickness of 2 μm on a masked side surface, it wasdried at 100° C. for 15 seconds. Subsequently, a non-stretchedpolypropylene film having a thickness of 25 μm was further adhered onthe second peripheral adhesive agent and left for three days in aconstant temperature reservoir of 40° C. to perform curing. Thereafter,at the position corresponding to the outer periphery of the polyesteradhesive tape (outer periphery of a negative electrode active materiallayer 13), only the non-stretched polypropylene film layer was cut.Then, the non-stretched polypropylene film (only the inner portion ofthe cut portion; only the region corresponding to the adhesive tape) wasremoved together with the polyester adhesive tape, so that the surfaceof the negative electrode active material layer 13 was exposed.

Next, three pieces of negative electrode side sheet bodies 62 eachhaving a size of 85 mm×54 mm (see FIG. 7) were produced by cutting alongthe position positioned outward by 5 mm from the outer periphery of theexposed surface of the negative electrode active material layer 13.

The width of the second thermoplastic resin layer 14 formed by thenon-stretched polypropylene film was 5 mm.

(Production of Thin Power Storage Device 1)

Next, a porous wet separator 21 having a length 85 mm×a width 54 mm×athickness 8 μm was arranged between the positive electrode side sheetbody 61 and the negative electrode side sheet body 62 (see FIG. 7). Atthis time, the positive electrode side sheet body 61 was arranged suchthat the positive electrode active material layer 3 exists on theseparator 21 side, and the negative electrode side sheet body 62 wasarranged such that the negative electrode active material layer 13exists on the separator 21 side.

Next, in a state in which the separator 21 was sandwiched and held byand between the positive electrode side sheet body 61 and the negativeelectrode side sheet body 62, the three sides thereof among the foursides as seen in a plan view were sandwiched and pressed with a pair ofheated plates of 200° C. from the above and below at a pressure of 0.2MPa for three seconds to thereby seal and join the three sides.

Next, an electrolyte in which lithium hexafluorophosphate (LiPF₆) wasresolved at a concentration of 1 mol/L in a mixed solvent in whichethylene carbonate (EC), dimethyl carbonate (DMC), ethylmethyl carbonate(EMC) were blended at an equal amount volume ratio was injected by 0.5mL from a non-sealed one side between the separator 21 and the positiveelectrode active material layer 3 and between the separator 21 and thenegative electrode active material layer 13 using a syringe. Thereafter,vacuum sealing was performed to perform provisional sealing.

Thereafter, charging was performed until a battery voltage 4.2 V wasgenerated to cause generation of gases from the electrodes, theseparator, etc. Thereafter, in a discharging state of 3.0 V and underreduced pressure of 0.086 MPa, the remaining one un-sealed side wassandwiched and pressed by and between a pair of heated plates of 200° C.at a pressure of 0.2 MPa for three seconds to perform heat sealing.Thus, the four sides were completely sealed and joined, so that a cardtype thin power storage device (thin type simulated battery) 1 having abattery capacity of 20 mAh as shown in FIGS. 1 and 2 was obtained.

Example 2

A card type thin power storage device (thin simulated battery) 1 havinga battery capacity of 20 mAh as shown in FIGS. 1 and 2 was obtained inthe same manner as in Example 1 except that a hard stainless steel foil(SUS304) was used as the second metallic foil layer of the negativeelectrode part in place of a hard copper foil.

Example 3

A card type thin power storage device (thin simulated battery) 1 havinga battery capacity of 20 mAh as shown in FIGS. 3 and 4 was obtained inthe same manner as in Example 1 except that the following additionalstructure was further added to the positive electrode side sheet body 61obtained in Example 1.

The following additional structure was added as explained below. Thatis, masking was performed by adhering a polyester adhesive tape having asize of 5 mm×5 mm to the central portion of the other surface (theopposite side surface opposite to the side in which the positiveelectrode active material layer 3 was formed) of the hard aluminum foil(first metallic foil layer) 2 of the positive electrode side sheet body61 obtained in Example 1. Thereafter, to the entire surface side towhich masking was performed, a polyester urethane-based adhesive agent(third adhesive agent layer) 41 was applied by a thickness of 2 μm anddried at 100° C. for 15 second. Subsequently, a biaxially stretchedpolyester film (first insulation resin film layer) 8 having a thicknessof 12 μm was adhered on the third adhesive agent layer 41 and left in aconstant temperature reservoir of 40° C. for three days to performcuring. Thereafter, cutting was formed only in the biaxially stretchedpolyester film at the position corresponding to the outer periphery ofthe polyester adhesive tape, and then the part of the biaxiallystretched polyester film was removed together with the polyesteradhesive tape to form an opening 8X at the central portion of thebiaxially stretched polyester film, so that the first metal exposedportion 9 having a size of 5 mm×5 mm was exposed at the central portionof the other surface of the hard aluminum foil (first metallic foillayer) 2. Thus, the positive electrode side sheet body 61 shown in FIG.7 was obtained.

Further, in the same manner, masking was performed by adhering apolyester adhesive tape having a size of 5 mm×5 mm to the centralportion of the other surface (the opposite side surface opposite to theside in which the negative electrode active material layer 13 wasformed) of the hard copper foil (second metallic foil layer) 12 of thenegative electrode side sheet body 62 obtained in Example 1. Thereafter,to the entire surface side to which masking was performed, a polyesterurethane-based adhesive agent (fourth adhesive agent layer) 42 wasapplied by a thickness of 2 μm and dried at 100° C. for 15 second.Subsequently, a biaxially stretched polyester film (second insulationresin film layer) 18 was adhered on the fourth adhesive agent layer 42and left in a constant temperature reservoir of 40° C. for three days toperform curing. Thereafter, cutting was formed only in the biaxiallystretched polyester film at the position corresponding to the outerperiphery of the polyester adhesive tape, and then the part of thebiaxially stretched polyester film was removed together with thepolyester adhesive tape to form an opening 18X at the central portion ofthe biaxially stretched polyester film, so that the second metal exposedportion 19 having a size of 5 mm×5 mm was exposed at the central portionof the other surface of the hard copper foil (second metallic foillayer) 12. Thus, the negative electrode side sheet body 62 shown in FIG.7 was obtained.

Using the positive electrode side sheet body 61 and the negativeelectrode side sheet body 62 obtained as mentioned above, in the samemanner as in Example 1, a production process of the thin power storagedevice was performed to thereby obtain a thin power storage device (thintype simulated battery) 1 shown in FIGS. 3 and 4.

Comparative Example 1

Initially, as explained below, laminated packaging materials 151 and152, a positive electrode tab lead 131, and a negative electrode tablead 141 were prepared.

(Laminated Packaging Material)

A polyester film having a thickness of 12 μm was adhered to one surfaceof a soft aluminum foil (A8021 soft aluminum foil classified into JISH4160) having a thickness of 20 μm via a polyester urethane-basedadhesive agent, and a polypropylene film having a thickness of 25 μm wasadhered to the other surface of the soft aluminum foil via a polyolefinadhesive agent. Thereafter, it was cured for three days in a constanttemperature reservoir of 40° C. and then cut to thereby obtain alaminated packaging materials 151 and 152 each having a size of 85 mm×54mm.

(Positive Electrode Tab Lead)

An insulation film 132 made of a maleic anhydride-modified polypropylenefilm (fusing point: 140° C., melt flow rate (MFR): 3.0 g/10 minutes)having a length 10 mm, a width 5 mm, and a thickness 50 μm wassandwiched and pressed by heat seal on both surfaces of the partialregion inner than the position within 5 mm from a longitudinal one endof a hard aluminum plate (A1050 hard aluminum foil classified into JISH4000) having a length 40 mm, a width 3 mm, and a thickness 500 μm, sothat the positive electrode tab lead 131 shown in FIGS. 10A, 10B, and10C was obtained.

(Negative Electrode Tab Lead)

An insulation film 142 made of a maleic anhydride-modified polypropylenefilm (fusing point: 140° C., melt flow rate (MFR): 3.0 g/10 minutes)having a length 10 mm, a width 5 mm, and a thickness 50 μm wassandwiched and pressed by heat seal on both surfaces of the partialregion inner than the position within 5 mm from a longitudinal one endof a nickel plate having a length 40 mm, a width 3 mm, and a thickness500 μm, so that the negative electrode tab lead 141 shown in FIGS. 10A,10B, and 10C was obtained.

(Production of Thin Power Storage Device 160)

After applying a binder solution in which polyvinylidene fluoride (PVDF)as a binder was dissolved in a dimethylformamide (DMF) as a solvent toone surface (entire surface) of a hard aluminum foil (A1100 hardaluminum foil classified into JIS H4160) having a length 20 cm, a width30 cm and a thickness 15 μm, it was dried at 100° C. for 30 seconds toform a binder layer having a thickness of 0.5 μm after drying.

After applying a paste in which 60 parts by mass of a positive electrodeactive material having lithium cobalt oxide as a main component, 10parts by mass of polyvinylidene fluoride (PVDF) as a binder and anelectrolyte retention agent, 5 parts by mass of acetylene black(conductive material), and parts by mass of N-methyl-2-pyrrolidone (NMP)(organic solvent) were kneaded and dispersed to a surface of a binderlayer of the hard aluminum foil, it was dried at 100° C. for 30 minutes,and then hot-press was performed. Thus, a positive electrode activematerial layer having a density of 4.8 g/cm³ and a thickness of 30.2 μmafter drying was formed. Thereafter, it was cut to obtain a positiveelectrode 122 having a size of 75 mm×45 mm.

A longitudinal one end portion of the positive electrode tab lead 131(one end portion to which the insulation film 132 was attached) wasoverlapped on a longitudinal one end portion of the active materialnon-applied surface (opposite side surface to which the positiveelectrode active material layer was formed) of the positive electrode122, and the overlapped portion was welded with an ultrasonic welder(see FIG. 10A). In FIG. 10A, “133” denotes a welded portion.

After applying a binder solution in which polyvinylidene fluoride (PVDF)as a binder was dissolved in a dimethylformamide (DMF) as a solvent toone surface (entire surface) of a hard copper foil (C1100R hard copperfoil classified into JIS H3100) having a length 20 cm, a width 30 cm anda thickness 15 μm, it was dried at 100° C. for 30 seconds to form abinder layer having a thickness of 0.5 μm after drying.

After applying a paste in which 100 parts by mass of a negativeelectrode active material having carbon powder as a main component, 5parts by mass of polyvinylidene fluoride (PVDF) as a binder and anelectrolyte retention agent, 10 parts by mass of a copolymer ofhexafluoropropylene and maleic anhydride, 3 parts by mass of acetyleneblack (conductive material), and 25 parts by mass ofN-methyl-2-pyrrolidone (NMP) (organic solvent) were kneaded anddispersed to a surface of a binder layer of the hard copper foil, it wasdried at 100° C. for 30 minutes, and then hot-press was performed. Thus,a negative electrode active material layer having a density of 1.5 g/cm³and a thickness of 20.1 μm after drying was formed. Then, it was cut tothereby obtain a negative electrode 123 having a size of 75 mm×45 mm.

A longitudinal one end portion of the negative electrode tab lead 141(one end portion to which the insulation film 142 was attached) wasoverlapped on a longitudinal one end portion of the active materialnon-applied surface (opposite side surface to which the negativeelectrode active material layer was formed) of the negative electrode123, and the overlapped portion was welded with an ultrasonic welder(see FIG. 10A). In FIG. 10A, “143” denotes a welded portion.

Next, as shown in FIG. 10A, the separator 121 was sandwiched between thepositive electrode 122 to which the positive electrode tab lead 131 wasjoined and the negative electrode 123 to which the negative electrodetab lead 141 was joined in a laminated manner, so that an electrode mainbody 110 was structured (see FIG. 10B). At this time, the positiveelectrode active material layer was positioned on the separator 121 sideof the positive electrode 122 and the negative electrode active materiallayer was positioned on the separator 121 side of the negative electrode123, and the tab leads 131 and 141 were positioned so as to bepositioned oppositely in the right and left direction so that thepositive electrode tab lead 131 and the negative electrode tab lead 141were not overlapped (see FIG. 10B).

Next, as shown in FIG. 10B, the electrode main body 110 was arrangedbetween a pair of upper and lower laminated packaging materials 151 and152. At this time, the polypropylene films (heat sealing layers) of thelaminated packaging materials 151 and 152 were arranged so as to bepositioned on the inner side (electrode main body 110 side).

Thereafter, in a state in which the electrode main body 110 wassandwiched and held by and between the pair of upper and lower laminatedpackaging materials 151 and 152, the three sides thereof among the foursides as seen in a plan view were sandwiched and pressed with a pair ofheated plates of 200° C. from the above and below at a pressure of 0.2MPa for three seconds to thereby seal and join the three sides.

Next, an electrolyte in which lithium hexafluorophosphate (LiPF6) wasresolved at a concentration of 1 mol/L in a mixed solvent in whichethylene carbonate (EC), dimethyl carbonate (DMC), ethylmethyl carbonate(EMC) were blended at an equal amount volume ratio was injected by 0.5mL from a non-sealed one side between the separator 121 and the positiveelectrode active material layer and between the separator 121 and thenegative electrode active material layer using a syringe. Thereafter,vacuum sealing was performed to perform a provisional sealing.

Thereafter, charging was performed until a battery voltage 4.2 V wasgenerated to cause generation of gases from the electrodes, theseparator, etc. Thereafter, in a discharging state of 3.0 V and underreduced pressure of 0.086 MPa, the remaining one un-sealed side wassandwiched and pressed by and between a pair of heated plates of 200° C.from the above and below at a pressure of 0.2 MPa for three seconds toperform heat sealing. Thus, the four sides were completely sealed andjoined, so that a card type thin power storage device (thin typesimulated battery) 160 having a battery capacity of 20 mAh as shown inFIG. 10C was obtained.

TABLE 1 Each structure of card type battery Positive electrode Negativeelectrode Evaluation Results (after press) (after press) ThinnessThickness Thickness Thickness Discharge capacity ratio (%) of active ofactive of the After After After Inner material material Lightnessthickest Immediately leaving leaving leaving resistance Density layerDensity layer Mass portion after at at at value (g/cm³) (μm) (g/cm³)(μm) (g)

charging 40° C. 60° C. 80° C. (mΩ) Ex. 1 4.8 30.2 1.5 20.1 1.541 80 10098 96 92 35 Ex. 2 4.8 30.2 1.5 20.1 1.453 80 100 95 94 92 34 Ex. 3 4.830.2 1.5 20.1 1.602 104 100 98 96 92 35 Comp. 4.8 30.2 1.5 20.1 2.235148 — 96 95 92 42 Ex. 1

indicates data missing or illegible when filed

For each thin power storage device (thin simulated battery) of Examples1 to 3 and Comparative Example 1, evaluations were made based on thefollowing evaluation method.

<Evaluation Method of Lightness and Thinness>

The entire mass (g) of each thin power storage device was measured toinvestigate the lightness, and the thickness (μm) of the thickestportion of the thin power storage device was measured to investigate thethinness.

<Evaluation Method of Discharge Capacity Ratio>

For each thin power storage device, four samples were preparedrespectively. A discharge capacity ratio (discharge capacity ratioimmediately after charging) when the first sample of each thin powerstorage device was charged with a charging current of 10 mA until itbecomes 4.2 V and then discharged to 3.0 V at the current value of 10 mAwas measured, and the internal resistance value of the thin powerstorage device was measured using an internal resistance measuringinstrument.

The “discharge capacity ratio immediately after charging” in eachExample is a value calculated by the following calculating formula.

Discharge capacity ratio (%)=(Discharge capacity measured valueimmediately after charging of each Example)÷(Discharge capacity measuredvalue immediately after charging of Comparative Example 1)×100

(Discharge Capacity Ratio after Leaving at 40° C.)

A discharge capacity ratio when the second sample of each thin powerstorage device was charged with a charging current of 10 mA until itbecomes 4.2 V and left in a constant temperature reservoir at 40° C. forseven days, then taken out from the reservoir, and discharged to 3.0 Vat the current value of 10 mA (discharge capacity ratio immediatelyafter charging at 40° C.) was measured.

The “discharge capacity ratio after leaving at 40° C.” in each Exampleis a value calculated by the following calculating formula.

Discharge capacity ratio after leaving at 40° C. (%)=(Discharge capacitymeasured value after leaving at 40° C. of each Example)÷(Dischargecapacity measured value immediately after charging of ComparativeExample 1)×100

While, the “discharge capacity ratio after leaving at 40° C.” inComparative Example 1 is a value calculated by the following calculatingformula.

Discharge capacity ratio after leaving at 40° C. (%)=(Discharge capacitymeasured value after leaving at 40° C. of Comparative Example1)÷(Discharge capacity measured value immediately after charging ofComparative Example 1)×100

(Discharge capacity ratio after leaving at 60° C.)

A discharge capacity ratio when the third sample of each thin powerstorage device was charged with a charging current of 10 mA until itbecomes 4.2 V and left in a constant temperature reservoir at 60° C. forseven days, then taken out from the reservoir, and discharged to 3.0 Vat the current value of 10 mA (discharge capacity ratio after leaving at60° C.) was measured. The calculating formula of “discharge capacityratio after leaving at 60° C.” conform to the calculating formula of theaforementioned “discharge capacity ratio after leaving at 40° C.”

(Discharge Capacity Ratio after Leaving at 80° C.)

A discharge capacity ratio when the third sample of each thin powerstorage device was charged with a charging current of 10 mA until itbecomes 4.2 V and left in a constant temperature reservoir at 80° C. forseven days, then taken out from the reservoir, and discharged to 3.0 Vat the current value of 10 mA (discharge capacity ratio after leaving at80° C.) was measured. The calculating formula of “discharge capacityratio after leaving at 80° C.” conform to the calculating formula of theaforementioned “discharge capacity ratio after leaving at 40° C.”

As will be apparent from Table 1, the thin power storage devices ofExamples 1 to 3 are lighter and thinner as compared with a conventionaltype of Comparative Example 1. In the power storage device ofComparative Example 1, since tab leads are required (tab leads exist),as compared with Examples 1 to 3, the mass is relatively large, and theheat sealed portion in which the tab leads 131 and 141 are sandwiched bythe upper and lower packaging materials 151 and 152 is considerablyincreased in thickness.

Further, the discharge capacity ratio immediately after charging is100%, and the discharge capacity ratio after leaving at 80° C. is 92%,which is a level causing no problem as compared with a lithium-ionbattery armored by a common metallic can. Further, the internalresistance value is also reduced. It is understood that the thin powerstorage device of the present invention is reduced in weight andthickness, and is excellent in basic performance as a lithium-ionbattery.

TABLE 2 Voltage Capacity value (V) (mAh) Example 1 4.192 19.6 Module*¹⁾11.85 19.8 *¹⁾Module in which three batteries of Example 1 are connectedin series.

Next, a module in which three thin power storage devices of Example 1were laminated in series in a manner shown in FIGS. 5 and 6 wasproduced. These were connected in series without providing the positiveelectrode side conductive layer 51, and the negative electrode sideconductive layer 52.

As will be apparent from Table 2, the voltage of the module was 11.85 Vand the capacity value was 19.8 mAh. Thus, it is understood that themodule in which a plurality of thin power storage devices of the presentinvention were connected in series is excellent in basic performance asa lithium-ion battery.

The thin power storage device according to the present invention can beexemplified by, for example, a thin electrochemical device such as athin lithium secondary battery (a lithium-ion battery, a lithium polymerbattery, etc.), a thin lithium-ion capacitor, and a thin electric doublelayer capacitor.

The thin power storage device according to the present invention can bepreferably used as, for example, a backup power supply for IC cards, butnot limited to it. Further, although the thin power storage device ofthe present invention can be preferably used as a power source forvarious mobile electronic devices such as a smart phone or a tablet-typeterminal by connecting a plurality of thin power storage devices in alaminated manner, but not limited to such a usage.

Further, the power storage device module 50 in which a plurality of thinpower storage devices 1 of the present invention are laminated in thethickness direction and structured into a cylindrical shape as shown inFIGS. 9A and 9B can be used as, for example, a battery for an electroniccigarette, a battery for a pen light, an auxiliary battery for apersonal computer, etc.

The present invention claims priority to Japanese Patent Application No.2014-165690 filed on Aug. 18, 2014 and Japanese Patent Application No.2015-137011 filed on Jul. 8, 2015, the entire disclosure of which isincorporated herein by reference in its entirety.

The terms and descriptions used herein are used only for explanatorypurposes and the present invention is not limited to them. The presentinvention allows various design-changes falling within the claimed scopeof the present invention unless it deviates from the spirits of theinvention.

1. A production method of a thin power storage device, comprising: astep of preparing a positive electrode side sheet body including a firstmetallic foil layer, a positive electrode active material layerlaminated on a partial region of one surface of the first metallic foillayer, and a first thermoplastic resin layer provided at a peripheralportion of the one surface of the first metallic foil layer on which thepositive electrode active material layer is not formed; a step ofpreparing a negative electrode side sheet body including a secondmetallic foil layer, a negative electrode active material layerlaminated on a partial region of one surface of the second metallic foillayer, and a second thermoplastic resin layer provided at a peripheralportion of the one surface of the second metallic foil layer on whichthe negative electrode active material layer is not formed; a step ofpreparing a separator; and a step of heat-sealing the firstthermoplastic resin layer of the positive electrode side sheet body andthe second thermoplastic resin layer of the negative electrode sidesheet body in a state in which the positive electrode side sheet bodyand the negative electrode side sheet body are in contact with eachother via respective thermoplastic resin layers and the separator issandwiched by and between the positive electrode active material layerand the negative electrode active material layer.
 2. The productionmethod of a thin power storage device as recited in claim 1, wherein thefirst thermoplastic resin layer is formed by a thermoplastic resinunstretched film and the second thermoplastic resin layer is formed by athermoplastic resin unstretched film.